使用承诺，类型"{}"上的属性不存在 [英] Property does not exists on type '{}' using Promises

问题描述

我正在访问从已解决的承诺返回的对象的属性.

I am accessing a property of an object returned from a resolved promise.

return new Promise((resolve) => {
    // Get result
    resolve(result)
}).then(r => console.log(r.id))

Typescript编译代码并且代码可以工作，但是我的IDE抱怨r.id

Typescript compiles the code and the code works but my IDE is complaining about r.id

[ts]属性'id'在类型'{}'上不存在.

[ts] Property 'id' does not exist on type '{}'.

处理此问题的"TypeScript"方法是什么? 这个问题似乎有相同的问题，但我无法理解给定的解决方案. 此答案讨论了使用接口，但不确定如何将其应用于Promise的then()功能

What is the 'TypeScript' method of dealing with this? This question seems to have the same issue but I cannot understand the given solutions. This answer talks about using interfaces but im not sure how I would apply that to the then() function of a Promise

推荐答案

Typescript不能通过使用resolve来区分Promise的结果类型，您需要将结果类型显式指定为Promise的通用参数:

Typescript will not be able to tell the result type of the Promise by the usage of resolve, you need to specify the result type explicitly as a generic parameter to Promise:

new Promise<{ id: string }>((resolve) => {
    // Get result
    resolve(result)
}).then(r => console.log(r.id))

您可以用任何类型替换{ id: string }，因为奖励打字稿将检查是否以正确的结果类型调用了resolve.

You can replace { id: string } with any type, as bonus typescript will check that resolve is called with the correct result type.

修改 我假设不是// Get result，而是有一些更复杂的代码需要使用Promise构造函数.如果您已经知道结果，则可以使用Promse.resolve(result)，它会按照@BenjaminGruenbaum在注释中指出的那样正确键入Promise

Edit I am assuming that instead of // Get result there is some more complicated code that requires use of the Promise constructor. If you already know the result, you can just use Promse.resolve(result) which will type the promise correctly as @BenjaminGruenbaum pointed out in the comments

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